Apparatus for anchoring autologous or artificial tendon grafts in bone

ABSTRACT

An anchor assembly for autologous or artificial tendon grafts comprises an insertion element and a stabilizing element. The insertion element has a stem and a head containing an aperture large enough to receive a graft. The stabilizing element is adapted to be embedded in bone, and comprises a sleeve with a cavity arranged to receive and hold the insertion element stem. In use, the stabilizing element is affixed in the bone, and the stem of the insertion element is placed therein. A tendon graft may be secured to the insertion element either before or after its placement in the stabilizing element. Two such anchors may be linked with one or multiple grafts, in either a two-ply or four-ply arrangement.

REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of, prior of and is acontinuation-in-part of U.S. patent application Ser. No. 08/887,5809filed Jul. 3, 1997 (Attorney Docket: 0383311-0076), and of U.S. patentapplication Ser. No. 08/754,566, filed Nov. 21, 1996 (Attorney Docket;0383311-0058).

BACKGROUND OF THE INVENTION

[0002] This invention pertains to surgical systems and, moreparticularly, apparatus and methods for attaching autologous orartificial tendon grafts to bone. The invention has application in, forexample, repair of the anterior cruciate ligament (ACL) of the knee. Itmay also be used, for example, for repair of other ligaments, such as ofthe elbow or ankle.

[0003] It is not uncommon for ligaments and other soft tissue to tear ordetach from bone. Athletes, for example, often suffer tears or otherinjuries to the anterior cruciate ligament, one of the ligamentsconnecting the femur. (thigh bone) and the tibia (shin bone) at thecenter of the knee joint. The ACL, which limits hyperextension of theknee and prevents the backward sliding of the femur on the tibialplateau, may be injured when the knee is twisted beyond the normal rangeof motion, e.g., when the knee is twisted while bending and weavingduring skiing and other sports activities. ACL injuries may take theform of total or partial tears.

[0004] Reconstruction is the most common form of surgery for injuries tothe ACL and involves replacing the ACL with a graft of autologous orartificial tendon. An autologous tendon graft may be “harvested” fromthe patient's patellar ligament, which is part of the common tendon ofthe quadriceps femoris, connecting the patella to the tibia. Analternative autologous tendon graft may be harvested from thesemitendinosus tendon, which runs posteriorly and medially along thethigh and which connects the upper femur to the tibia.

[0005] Traditionally, patellar grafts are harvested with attached boneplugs that can be securely fixed at the ends of a bone tunnel drilledthrough the tibia and femur using a metallic interference screw, a metalscrew and washer, or buttons. Drawbacks associated with the use of thepatellar tendon-include difficulties in harvesting the tendon andpostoperative complications.

[0006] More recent success has been achieved using one or more strandsof the triple-stranded semitendinosus, tendon, which can be harvestedwith minimal-post-operative complications. The strands can be used aloneor in combination with the gracilis tendon, which anatomically runsparallel along the thigh to the semitendinosus tendon. Althoughsemitendinosus tendons are increasingly used in ACL repair, they aredifficult to attach to bone, due in part to the absence of associatedbone plugs.

[0007] The art suggests, several techniques for attaching thesemitendinosus tendon to bone in ACL repair. One such technique involvessuturing the tendon to a button or staple on the exterior of the bone.Drawbacks associated with this method include stretching or failure ofthe suture, which may be subjected to tensile forces ranging from 30-50pounds.

[0008] Another technique involves attaching a tendon graft to bone usingmetallic screws. Although such metal screws demonstrate stable fixationand good tensile strength, they have, a number of drawbacks. Theseinclude distortion of post-operative radiological studies, an allergicor rejection reaction resulting from metal sensitivity associated withpermanently implanted metal screws, and the potential need foradditional operations for removal or replacement.

[0009] Another technique involves attaching a tendon graft to an anchoraffixed within a tunnel drilled in the bone. One anchor intended forthis use is the Mitek Ligament Anchor available from Mitek SurgicalProducts, Inc. That anchor includes prongs that lodge into the boneafter the anchor has been pulled into position by a suture. A drawbackof that anchor is that it must be lodged in the cortical layer near thesurface of the femur and therefore necessitates the use of long tendonsegments. In addition, the anchor's design necessitates that it befabricated from metal to ensure sufficient holding strength.

[0010] An object of this invention is to provide improved surgicalsystems, and more particularly, improved methods and apparatus forattaching autologous or artificial tendon grafts to bone.

[0011] Another object of this invention is to provide improved methodsand apparatus for attachment of autologous or artificial tendon grafts(e.g., for ACL repair) that are in which the attachment means can befabricated from polymers or bioabsorbable materials, without the use ofmetals.

[0012] A related object of this invention is to provide methods andapparatus for attachment of autologous and artificial tendons thatminimize or eliminate the risk of graft pullout normally associated withACL or other reconstructive orthopedic surgery.

SUMMARY OF THE INVENTION

[0013] The above objects are among those met by the invention, whichprovides improved methods and apparatus for attaching autologous orartificial tendon grafts to bone, e.g., during ligament and otherreconstructive surgery, including ACL reconstruction. These allowanchoring the tendon graft in the bone, without metal and withoutplacing undue load on sutures.

[0014] In one aspect, an assembly according to the invention comprisesan insertion element and a stabilizing element. The stabilizing elementhas an outer surface adapted for interference fit with a bone hole. Theinsertion element includes an aperture through which a graft may bethreaded or attached, and a stem adapted to be inserted into andretained in a cavity in the stabilizing element, e.g., by aninterference fit. Additionally, the insertion element may comprise anaperture, slot, or barb, preferably at its distal end, to facilitate itsinsertion into the stabilizing element.

[0015] According to one aspect of the invention, the stabilizing elementhas a threaded outer surface that can be securely turned into the bone.In addition, the stabilizing element can have an inner bore that issmaller than the outer diameter of the insertion element, such thatplacement of the latter into the former causes the stabilizing elementto deformably expand or otherwise obtain a still stronger pressure fitwith the bone hole.

[0016] In another aspect, the invention provides a stabilizing elementthat has a flanged head that rests on the surface of the bone, outsideof the bone hole, and that prevents the element from entering the bonehole beyond a certain point.

[0017] In further aspects of the invention, the insertion andstabilizing elements comprise bio-compatible materials. These avoidadverse biological reactions to the elements, as well as the need for asecond surgical procedure to remove the elements.

[0018] A related aspect of the invention comprises a system comprisingtwo or more anchoring assemblies as described above. Such a system canbe used with one or more natural or artificial crafts to repair orstrengthen a skeletal bone or joint. In ACL repair, for example, onestabilizing element: can be placed at one end of a bone hole drilledinto the femur, and the other stabilizing element can be placed in analigned tunnel drilled into the tibia. The first and second insertionelements can then be joined by the graft and inserted into theirrespective stabilizing elements. The stabilization element placed in thefemur can be of the type having a threaded outer surface, while thatemplaced in the tibia can be of the type having a flanged head. Such aconfiguration exploits the strong cancellous matter in the femur, whichis well adapted to holding screw threads, and relies on the surface ofthe tibia to ensure a hold there.

[0019] Another aspect of the invention comprises a method for anchoringa graft in bone, for example for the replacement of a torn ligament. Inthis method, a tunnel or opening is drilled into the bone, and astabilization element of the type described above is placed therein. Agraft is looped through the head of an insertion element which, in turn,is inserted into the stabilization element. The insertion andstabilization elements may incorporate various structures designed tomore effectively dispose and/or secure them in the bone tunnel, asdescribed above. For example, the stabilization element may comprise aflanged head which prevents it from being pulled into the bone tunnelwhen tension is applied to the tissue graft after insertion of theinsertion element.

[0020] In yet another aspect, the invention comprises a kit for securinga graft, e.g., for ACL replacement. The kit comprises two stabilizationelements adapted to be secured in bone. These can include, for example,a stabilization element adapted to be secured (e.g., in the femur) byscrew threads and a stabilization element adapted to be secured (e.g.,in the tibia) by a flange which prevents the element from being pulledthrough a bone hole. The kit further comprises two insertion elementsfor securing the graft to the stabilization elements. Each insertionelement is provided with an aperture at the head whereby an autologousor artificial tissue graft may be attached, as well as a stem adaptedfor insertion into a cavity in a stabilization element. These insertionelements may also comprise an aperture, slot, or barb, to facilitatetheir being pulled into the corresponding stabilizing element. The kitmay optionally include a graft, such as a length of artificial tendon ora length of actual semitendinosus tendon.

[0021] More generally, the invention also comprises a kit for connectingtwo or more bones with grafts, for example, for replacing ligaments ofthe ankle or elbow. In this aspect, the kit comprises at least twostabilization elements of the types described above of appropriate sizeand anchoring configuration for the bones in which they are intended tobe emplaced. The kit further comprises a comparable number of insertionelements of the types described above intended to be inserted into thestabilization elements, each of which comprises an aperture at the headsuitable for affixing a graft. The kit may optionally include one ormore lengths of artificial tissue, or it may be intended to be used withone or more autologous grafts.

[0022] Methods and apparatus of the instant invention overcomelimitations of prior art systems for affixing grafts to bone. Thetwo-piece apertured design enables construction of an anchor assembly toattach autologous or artificial tendon grafts securely within bonewithout the use of metal, and without placing the high loads on suturesthat are associated with sewing or tying grafts directly to bone.

[0023] Yet other aspects of the invention comprise methods for ligamentreconstruction, whereby various configurations of grafts are used toconnect bone anchors of the types described above, or other anchorscontaining apertures suitable for threading grafts. These methods employat least one graft having a filament extending from at least one of itsends. By way of example, this filament may be a suture which has beenwhip stitched to the end of a tendon graft.

[0024] The graft as emplaced according to this aspect of the inventionmay connect the bone anchors with two or four plies of graft material.In one two-ply configuration, a single graft is used. The graft isthreaded through the aperture of one bone anchor, and folded to bringits ends into proximity. The two ends are then affixed to the other boneanchor, preferably by sewing with the attached filament(s). The anchorscan be affixed in bone before or after threading of the grafts.

[0025] A related method, according to the invention also employs asingle graft. The graft is threaded through the apertures in both boneanchors, and the attached filament(s) are used to connect the two endsof the graft to one another. This is preferably done by sewing thefilaments at each end of the graft to the other end of the graft.

[0026] Another method according to the invention uses a single graft toconnect two bone anchors via four plies of graft material, rather thanby two plies as described in the previous two methods. According to thismethod, the graft (with at least one attached filament) is threadedthrough an aperture of a first bone anchor, and folded so that its endsare brought into proximity as described above. The two ends are thenthreaded through an aperture of a second bone anchor, and the graft isfolded again, to bring its ends in contact with the first anchor. Theattached filament(s) are used to connect the ends to the first anchor,preferably by sewing.

[0027] Other methods of attaching the grafts to bone anchors employmultiple grafts. These methods can lend additional strength to thereconstructed ligament. According to one such method, a graft withattached filament(s) is threaded through an aperture of one anchor andits ends are sewn to an aperture of another anchor, as described above.In addition, a second graft is threaded through the aperture of theanchor to which the first graft is sewn, and is sewn to the aperture ofthe anchor through which the first graft is threaded.

[0028] Another multiple-graft method of attachment threads two grafts(each with at least one attached filament) through the aperture of abone anchor. The two grafts are folded, and their ends are attached tothe aperture of a second bone anchor via the filaments. Each of thesemultiple-graft methods connects the anchors by four plies of graftmaterial.

[0029] These and other aspects of the invention are evident in thedrawings and in the description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] A more complete understanding of the invention may be attained byreference to the drawings, in which:

[0031]FIG. 1a depicts a frontal view of the bones of the knee and apartially torn anterior cruciate ligament (ACL);

[0032]FIG. 1b depicts a side view of a method for creating a steppedtunnel through the tibia and partially through the femur for insertionof an anchor assembly according to the invention;

[0033]FIG. 2 depicts a frontal view of a method for affixing a tendongraft into the tunnel of FIG. 1b in accord with the invention;

[0034]FIG. 3 depicts a detailed side view of an embedded anchor assemblyof the present invention;

[0035]FIGS. 4a-d depict detailed views of an anchor assembly of thepresent invention;

[0036]FIGS. 5a-5 c depict detailed views of the insertion element of ananchor assembly according to an alternate embodiment of the presentinvention;

[0037]FIG. 6 depicts a detailed view of the insertion of an assemblyaccording to yet another alternate embodiment of the present invention,this embodiment comprising the use of two stabilizing elements and twoinsertion elements;

[0038]FIG. 7 depicts a detailed view of a stabilizing element comprisinga flange;

[0039]FIG. 8 depicts a detailed view of a graft prepared for attachmentto one or more bone anchors; and

[0040]FIGS. 9a-9 f depict detailed views of grafts linking two boneanchors according to the methods of the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0041]FIG. 1a depicts a partially torn ligament of the knee, e.g., theanterior cruciate ligament (ACL) 1. In the illustration, the ACL isattached to a depression in the anterior intercondylar area (not shown)on the surface of the tibial plateau 5., This tibial attachment lies infront of the anterior intercondylar tubercle and is blended with theanterior extremity of the lateral meniscus (not shown). It passesupward, backward, and laterally to be fixed into the posterior part ofthe medial surface of the lateral condyle (not shown) of the femur 3.The tibia 2 and the patella 4 are also shown.

[0042]FIG. 1b depicts a method for creating a stepped tunnel 7 throughthe tibia 2 and partially through the femur 3 for insertion of an anchorassembly of the invention. In the illustration, a drill 6 is used by thesurgeon to drill a tunnel beginning at the anterior surface of the tibia2 and ending within the cancellous region of the femur 3. The drilltunnel 7 preferably will enter the femur 3 at or near the isometricpoint (not shown) close to the anatomical ACL attachment site inaccordance with the prior art. The angle of the drill tunnel is inaccord with that practiced in, the prior art for semitendinosus-styleACL repair. The stepped hole is formed by use of a stepped drill bitsuch that the ledge separating the wider and narrower diameter tunnelslies within the cancellous portion of the femur 3, e.g., within 10 mm to70 mm within the femur of the posterior part of the medial surface ofthe lateral condyle and, preferably, within approximately 45 mm of thatsurface. The drill tunnel 7 may terminate within the cancellous portionof the femur 3, or, in the alternative, the surgeon may elect initiallyto fully penetrate the femur 3 with a guide wire (not shown), leaving asmall exit aperture 9 on the opposing surface of the femur in accordancewith the prior art covering ACL reconstructive surgery. It will beappreciated by those skilled in the art that the above-describedinvention is not limited to embedding an anchor assembly in the femur 3but could also be practiced to embed an anchor in the tibia 2 or inbones comprising other joints, e.g., the ankle or elbow region, as wellas in individual or groups of bones otherwise requiring repair orsupport.

[0043]FIG. 2 depicts shows a graft anchor assembly 12 of the instantinvention embedded in bone, for example in the cancellous layer of thefemur 3. A tendon graft 110 is looped through the aperture (see detaileddrawing in FIG. 3) in an anchor assembly 12 with one or more free endsextending through other bone, for example, through the tibia 2.

[0044]FIG. 3 depicts in more detail an anchor assembly 12 in operatingposition embedded in the stepped bone tunnel. The autologous orartificial tendon graft 10 is looped through aperture 13 in the head ofthe insertion element 14. The stabilizing element 15 is embedded in thebone tunnel, for example by screwing into the stepped tunnel. In anotherembodiment, the stabilizing element may be secured by means of a flangewhich opposes tension on the tendon graft, as shown in FIG. 6. Theinsertion: element 14 is held in the stabilizing element 15 for exampleby compression fit, but could also be held by other interference fit,e.g., screwing (though, preferably by a thread) that requires twist,e.g., of lot more than 180° (so as to avoid twisting the tendon) or byratcheting or by other attachment mechanism for holding one element inanother without excessive twisting.

[0045]FIGS. 4a-d depict the anchor assembly in detail. FIG. 4a depictsthe stabilizing element 15 which comprises an elongated sleeve 19containing external protrusions 16, for example, external threads.Stabilizing element 15 has a cavity 17; for example an elongated axialchannel 17 extending at least partway from the proximal end ofstabilizing element 15. For example, axial channel 17 could extend fromthe proximal to the distal end of stabilizing element 15. Stabilizingelement has a flanged head 18. Stabilizing element 15 is comprised of abiocompatible material, for example, implant grade high densitypolyethylene, low density polyethylene (PE 6010 and PE 2030) andpolypropylene (13R9A and 23M2) all made by Rexene, Dallas, Tex. or of abioabsorbable material, for example poly-1-lactide or such as alactide-glycolide composition. It may also be comprised of a metal, suchas surgical implant grade steel.

[0046]FIG. 4a also depicts insertion element 14. Insertion element 14has an aperture 13 containing head 21 for retaining a ligamentreplacement. Stem head 21 has an aperture 13 of a size suitable forreceiving multiple strands of autologous and/or artificial tendon, butoptimally for receiving two or more strands of semitendinosus tendon.The aperture 13 may have dimensions 0.10 inches-0.35 inches (height) by0.05-0.30 inches (width), and, preferably approximately 0.220 inches by0.160 inches. Insertion element 14 has a stem 20, for example anelongated stem 20. The stem has protrusions 22 extending outwardly:Stem, protrusions 22 may be inflexible. In the illustrated embodiment,the diameter of stem 20 has a larger outer diameter than the innerdiameter of axial channel 17, such that stabilizing element 15 iscapable of holding the insertion element 14 by compression fit uponinsertion of the insertion element 14 into channel 17 of stabilizingelement 15. The insertion element 12 can be tapped into the stabilizing,element 15 with an emplacement device (not shown). Alternatively, theinsertion element can be configured to be screwed, ratcheted or placedin other interference fit within the stabilizing element. The insertionelement 12 is comprised of a biocompatible material, for example implantgrade high density polyethylene, low density polyethylene (PE 6010 andPE 2030) and polypropylene (13R9A and 23M2: all made by Rexene, Dallas,Tex.) or of a bioabsorbable material, for example poly-1-lactide or suchas a lactide-glycolide composition, it may also be comprised of a metal,such as surgical implant grade steel.

[0047]FIG. 4b depicts axial channel 17 which has a non-cylindricalcross-section (not shown), optimally a polygon such as a hexagon Othernon-cylindrical cross-sections such as a square or pentagon or even ovalconfigurations are also envisioned. A non-cylindrical cross-section ofthe axial channel 17 is designed such that a emplacement device (notshown) such as a driver (not shown) with a corresponding non-cylindricaldiameter can be inserted into a axial channel and turned such that theexternal threads 16 of the stabilizing element 15 are screwed into andgrip the bone. One such driver is, e.g., an Allen wrench.

[0048]FIG. 4c depicts insertion of the distal end of an insertionelement 12 into the axial channel 17 at the proximal end of astabilizing element 15. The diameter of elongated stem 20 is slightlygreater that the diameter of the non-cylindrical axial channel 17 of thestabilizing element. As a result as depicted in FIG. 4d, an elongatedstem 20 of the insertion element 12 is held tightly in stabilizingelement 15, for example by compression fit into stabilizing element 15embedded in a stepped bone hole.

[0049]FIG. 5a depicts an insertion element 10 that can be pulled intothe stabilizing element 15 (FIG. 4). As above, the insertion element 10has an aperture 12 containing a head for retaining a ligamentreplacement-and a stem 14 with outwardly expanding protrusions. Thediameter of stem is greater than the diameter of axial channel such thatstabilizing element 15 is capable of holding the insertion element bycompression fit upon insertion of the insertion element into the channelof the stabilizing element. Additionally, the insertion element 10contains a structure, e.g., aperture 16, suitable for receiving asuture, a wire or other device that can be used to pull the element 10into the stabilizing element 15 instead of, or in addition to, its beingtapped into that element 15.

[0050] The aperture 16 or other such structure can be located at anypoint on the insertion element 10 but is preferably located at thedistal end of the insertion element. Thus, for example, in an embodimentin which the stem of the insertion element is approximately 0.75 incheslong with a diameter of 0.16 inches, the aperture is located 0.05-0.20inches from the end of the insertion element and preferably 0.12 inchesfrom the distal end.

[0051] The aperture 16 (or other such structure) is sized sufficientlyto accommodate a suture, wire or other pulling device. Those of ordinaryskill in the art will of course appreciate that in lieu of an aperture,a slot, barb, hook (as shown in FIGS. 5b and 5 c) or any other structureby which the insertion element can be pulled, can be utilized.

[0052] An anchor assembly incorporating an insertion element 10 of FIG.5a is generally implanted as described above. In ACL reconstructivesurgery, for example, a tunnel is drilled at the anterior surface of thetibia and ending within the cancellous region of the femur. The drilltunnel preferably enters the femur at or near the isometric point closeto the anatomical ACL attachment site in accordance with the prior art.The angle of the drill tunnel is in accord with that practiced-in theprior art for semitendinosus-style ACL repair. A stepped hole is formedby use of a stepped drill bit such that the ledge separating the widerand narrower diameter tunnels lies within the cancellous portion of thefemur, e.g., within at least 10 mm to 70 mm within the femur of theposterior part of the medical surface of the lateral condyle and,preferably, approximately 45 mm of that surface,

[0053] Although the drill tunnel may terminate within the cancellousportion of the femur, a guide wire or K-wire is preferably used to fullypenetrate the femur, leaving a small exit aperture on the opposingsurface on the femur. The stabilizing element is then embedded in thedrilled bone tunnel, for example, by screwing it into the steppedtunnel. At this point, the K-wire (which is preferably equipped with aneyelet at its end) is used to thread a suture through the skin, bone andthrough the channel of the stabilizing element. The suture is thenlooped through the aperture, hook, barb, or slot, or other suchstructure in the insertion element. The insertion element is then pulledinto the stabilizing element using that suture. Those skilled in the artwill appreciate that a wire, hook or other such apparatus can be used inplace of the aforementioned suture.

[0054]FIG. 6 depicts yet another embodiment of the invention, whichemploys two stabilizing elements and two insertion elements In Hisembodiment, a stepped tunnel is drilled in the bone, beginning at theanterior surface of the tibia 2 and ending within the cancellous regionof the femur 3, similar to the tunnel depicted in FIG. 1b. The surgeonmay elect initially to fully penetrate the femur 3 with a guide wire 26,leaving a small exit aperture 9 on the opposing surface of the femur inaccordance with the prior art covering ACL reconstructive surgery.

[0055] A first stabilizing element 15 is then inserted in the femoraltunnel as has been described above. Insertion elements 12 and 24 arejoined by a length of soft tissue 10, such as a tendon graft, and thefirst insertion element 12 is inserted into the stabilizing element 15,for example by pushing into the stabilizing element 15, or by pullingwith a suture, wire, or other device 26 on a small aperture, slot, barbor hook on the insertion element 12. The second insertion element 24 ispushed into the bone tunnel, and then the second stabilizing element 28is placed-in the bone tunnel. In the preferred embodiment depicted inFIG. 6, the second stabilizing element 28 comprises a flange 30 whichlimits the extent to which the stabilizing element can be pulled intothe bone tunnel, e.g., by the tendon graft. This element is alsodepicted in FIG. 7 and is further discussed below. In other embodiments,the second stabilizing element may be secured by means of screw threads,an interference fit, or other methods known in the art. Finally, thesecond insertion element 24 is inserted into the second stabilizingelement 28. In the preferred embodiment depicted in FIG. 6, the secondinsertion element is inserted into the second stabilizing element bypulling with a suture, wire, or other device 32 on a small aperture,slot, barb, or hook on the second insertion element 24.

[0056] In an embodiment for ACL replacement for an adult, the firststabilizing element is typically of a length 20 mm, an outer diameter of8 mm, and an inner diameter of 3.5 mm. The first insertion element istypically of a length 40 mm and a diameter 8 mm. If the insertionelement is equipped with an aperture whereby it may be pulled into thestabilizing element, that aperture has a typical diameter of 1 mm. Theaperture for attachment of the tendon graft is typically about 5 mm×8mm. The length of the tendon graft between the insertion elements isusually about 40 mm. Those skilled in the art will appreciate that theforegoing dimensions are supplied merely by way of example and thatstabilization and insertion elements of sizes suited for other bones,joints and grafts can be used as well.

[0057] The surgeon can adjust the tension on the tendon graft bycontrolling the extent to which the insertion elements are inserted intothe stabilizing elements. Insertion elements are typically designed sothat full strength hold of the insertion element in the stabilizingelement is obtained when the insertion element is inserted at leasthalfway into the stabilizing element. Thus, the depth of each insertionelement is adjustable over a length of 10 mm for this preferredembodiment.

[0058] The second stabilizing element 28 of FIG. 6 is also illustratedin FIG. 7. This element comprises an elongated body 29, having a channel31 for receiving an insertion element. The stabilizing element alsocomprises a flange 30, which prevents the element from being pulledcompletely into the bone hole by tension on a graft attached to aninsertion element deployed in channel 3 l The flange 30 may beperpendicular to the elongated body 29, or may be at an oblique angle tothe body 29, as depicted in FIG. 7 The flange 30 may also be contouredto correspond to the shape of the outer surface of the bone in which itis to be emplaced. The surgeon may also elect to countersink the bonetunnel, so that the outer surface of the emplaced flange 30 is flushwith the surface of the surrounding bone. In this embodiment, it may bedesirable for the flange 30 to be tapered, having a thickercross-section at the intersection of the flange 30 with the body 29 thanat the outer edge of the flange 30.

[0059] When this embodiment is used in ACL repair as depicted in FIG. 6,the second stabilizing element has a typical length of 15 mm, an outerdiameter of 8 mm, and an inner diameter of 3.5 mm. The flange has atypical outer diameter of 12 mm, and a typical thickness of 1 mm. Thesecond insertion element has a length 40 mm and a diameter 8 mm. If thesecond insertion element is equipped with an aperture whereby it may bepulled into the stabilizing element, that aperture has a typicaldiameter of 1 mm. The aperture for attachment of the tendon graft istypically about 5 mm×8 mm. Those skilled in the art will appreciate thatthe foregoing dimensions are supplied merely by way of example and thatstabilization and insertion elements of sizes suited for other bones,joints and grafts can be used as well.

[0060] The second insertion element and second stabilizing element, likethe first elements, are comprised of a biocompatible material, forexample implant grade high density polyethylene, low densitypolyethylene (PE 6010 and PE 2030) and polypropylene (13R9A and 23M2)all made by Rexene, Dallas, Tex. or of a bioabsorbable material, forexample poly-l-lactide or such as a lactide-glycolide composition. Theseelements may also be comprised of a metal, such as surgical implantgrade steel.

[0061] It will be apparent to those skilled in the art that theabove-described invention is not limited to connecting the femur andtibia in an ACL reconstructive procedure, but could also be practiced tosupport or repair any bone or pair of bones with a length of softtissue, e.g., in the ankle or elbow region.

[0062] The invention further comprises methods for connecting at leasttwo bone anchors, for example those described above, with one or morelengths of graft material. FIG. 8 shows a graft 10 prepared according toa preferred embodiment of this aspect. The graft 10 may be an autologoustendon graft such as a length of semitendonosis or gracillis tendon, oran artificial graft. The graft 10 has a filament 40 (such as a suture)attached to at least one of its ends. In the preferred embodimentillustrated in FIG. 8, a suture 40 is whip-stitched to each end of thegraft.

[0063] The anchors may be connected with one or with multiple grafts, ineither a two-ply or four-ply configuration. Some configurationsaccording to the invention are illustrated in FIGS. 9a-9 f In FIG. 9a, asingle graft 10 is used to connect two anchors 42 and 44 in a two-plyconfiguration. A graft 10 prepared as illustrated in FIG. 8 is threadedthrough an aperture in one anchor 44, and then folded so that the twoends of the graft 10 can be tied and/or sewn to an aperture in the otheranchor 42 using the filament

[0064] A related embodiment is illustrated in FIG. 9b. In thisembodiment, the prepared graft 10 is threaded through apertures in eachof the two anchors 42 and 44. The sutures 40 attached to the preparedgraft are then tied, or, preferably, sewn, to connect the ends of thegraft 10. This embodiment is also a two-ply arrangement.

[0065] A four-ply connection between the anchors is achieved using asingle graft in the embodiment illustrated in FIGS. 9c and 9 d. Aprepared graft 10 is first threaded through one anchor 42, and folded tobring the ends of the graft 10 into contact. These two ends are thenthreaded through the other bone anchor 44. FIG. 9c illustrates theconfiguration of the graft at this point in its emplacement. The graft10 is then folded in half again, to bring the ends back to the firstanchor 42, and the ends are sewn and/or tied there with the attachedfilaments 40, as illustrated in FIG. 9d. Section A-A of that figureshows the four plies of graft material 10 which now connect the boneanchors.

[0066] Other embodiments which achieve a four-ply connection between theanchors using multiple tendon grafts are illustrated in FIGS. 9e and 9f. In the first of these, one graft 10, prepared as shown in FIG. 8, isthreaded through an aperture in a first anchor 44, and the sutures 40 atthe end of the graft are sewn and/or tied to an aperture in a secondanchor 42. A second graft 46 is then passed through the aperture in thesecond anchor 42, and sewn and/or tied to the aperture in the firstanchor 44 with its attached sutures 48. In the second embodiment,illustrated in FIG. 9f, two grafts 10 and 46 are threaded through anaperture in the first anchor 44, and these two grafts are both sewnand/or tied to the aperture in the second anchor 42 with their attachedsutures 40 and 48.

[0067] It will be apparent to one skilled in the art of ligamentreconstruction that each of the embodiments illustrated in FIGS. 9a-9 fhas different strengths and that the preferred configuration for aparticular use of the invention will depend on the ligament beingreplaced, the location and type of the bone anchors, and on whether thegraft is attached to the anchors before or after they are affixed to thebone.

[0068] Described above are apparatus and methods meeting the objects setforth above. Those skilled in the art will appreciate that theillustrated embodiments are shown and described by way of example only,and that other, methods and apparatus incorporation modificationstherein fall within the scope of the invention. For example, in additionto ACL reconstruction, the invention can be beneficially applied inconnection with other soft tissue-to-bone attachments using bonetunnels, such as (by way of non-limiting example) repair of ligamentsand tendons in other joints such as the elbow and ankle. In view of theforegoing.

What we claim is:
 1. An assembly for anchoring soft tissue or artificialgrafts in bone, comprising: an insertion element comprising a stem andan aperture-containing stem head proximal to said stem, said aperturebeing of a size sufficiently large to receive a soft tissue graft; and astabilizing element adapted to be embedded in bone comprising a sleevehaving a cavity, said cavity being arranged and constructed so as toreceive and hold said stem.
 2. An assembly for anchoring soft tissuegrafts in bone, comprising: an insertion element comprising a stem andan aperture-containing stem head proximal to said stem, said aperture,being of a size sufficiently large to receive a soft tissue graft; and astabilizing element adapted to be embedded in bone comprising a sleevehaving a cavity, said cavity being elongated and having an innerdiameter slightly smaller than an outer diameter of said stem, such thatsaid sleeve is capable of holding said stem by compression fit.
 3. Anassembly according to claims 1 or 2, wherein the insertion elementfurther comprises any of an aperture, slot, and, barb by which saidinsertion element can be pulled into said bone hole.
 4. An assemblyaccording to claim 3, wherein said any of an aperture, slot and barb isdisposed at the distal end of the insertion element.
 5. An assemblyaccording to claims 1 or 2, wherein at least one of said stem of saidinsertion element and said sleeve of said stabilizing element areelongate and have protrusions on their outer surfaces.
 6. An assemblyaccording to claim 5, wherein said protrusions on said stabilizingelement comprise, threading amenable to being screwed into an openingdrilled into bone.
 7. An assembly according to claims 1 or 2, whereinsaid stabilizing element comprises a flange at its distal end, wherebyupon embedding of the stabilizing element in the bone hole, the flangeis disposed at least partially outside the bone hole in a configurationwhereby it will oppose any further movement of the stabilizing elementinto the bone hole.
 8. An assembly according to claims 1 or 2, whereinsaid cavity comprises an axial channel, the cross-section of saidchannel being non-cylindrical, said axial channel extending betweenproximal and distal ends of said elongated sleeve.
 9. An assembly foranchoring soft tissue grafts in bone, comprising: an insertion elementcomprising an elongated stem and an aperture-containing stem headproximal to said stem, said aperture suitably sized for passage of asoft tissue graft therethrough; and a stabilizing element capable ofinsertion into an opening drilled into bone and comprising an elongatedsleeve having an axial channel, said channel having a diameter slightlysmaller than that of said elongated stem of said insertion element suchthat said stabilizing element will expand upon insertion of saidinsertion element into said channel.
 10. The assembly according to claim9, wherein the insertion element further comprises any of an aperture,slot, or barb by which said insertion element can be pulled into saidbone hole.
 11. An assembly according to claim 9 or 10, wherein across-section of said axial channel is non-cylindrical.
 12. The assemblyaccording to claim 11, wherein said stabilizing element can bedeformably expanded to obtain a pressure fit within a bone opening uponinsertion of said insertion element into said non-cylindrical apertureof said stabilizing element.
 13. The assembly according to claims 1, 2,9 or 10, wherein said insertion and stabilizing elements comprisebio-compatible material.
 14. The assembly according to claims 1, 2, 9 or10, wherein said stabilizing element has a fanged proximal end.
 15. Anassembly for anchoring soft tissue grafts into bone, comprising: aninsertion element comprising an elongated stem and aperture-containingstem head proximal to said stein, said aperture being of a sizesufficiently large to receive a soft tissue graft; and a stabilizingelement adapted to be embedded in bone comprising a elongated sleevewith external threads and an axial channel passing therethrough, saidaxial channel having a non-cylindrical cross-section such that anemplacement device can be inserted therein for screwing said threads ofsaid stabilizing element into said bone.
 16. The assembly according toclaim 15, wherein the insertion element further comprises any of anaperture, slot, and barb by which said insertion element can be pulledinto said bone hole.
 17. An assembly according to claim 10 or 16,wherein said any of an aperture, slot and barb is disposed at the distalend of the insertion element.
 18. The assembly of claim 1, 2, 9, or 15,further comprising: a second insertion element comprising a stem and anaperture-containing stem head proximal to said stem, said aperture beingof a size sufficiently large to receive a soft tissue graft; and asecond stabilizing element adapted to be embedded in bone comprising asleeve having a cavity, said cavity being arranged and constructed so asto receive and hold the stem of the second insertion element.
 19. Theassembly of claim 18, wherein at least one of the insertion element andthe second insertion element further comprises any of an aperture, slot,or barb by which said insertion element can be pulled into said bonehole.
 20. The assembly of claim 18, wherein at least one of thestabilizing element and the second stabilizing element comprises aflange at its distal end, whereby upon embedding of the stabilizingelement in the bone hole, the flange is disposed at least-partiallyoutside the bone hole in a configuration whereby it will oppose furthermovement of the stabilizing element into the bone hole
 21. A method foranchoring soft tissue within bone comprising: drilling an opening intobone; inserting into said bone opening a stabilizing element comprisingan elongated sleeve with an axial channel extending therethrough;threading soft tissue through an aperture in an insertion elementcomprising an aperture-containing stem head proximally located to anelongated stem, said stem having a diameter slightly larger than that ofsaid axial channel of said elongated sleeve; and inserting the distalend of said insertion element into proximal end of said stabilizingelement.
 22. A method according to claim 21, wherein said soft tissue isa tendon graft.
 23. A method according to claim 21, wherein the methodof drilling said opening comprises creating a stepped opening.
 24. Amethod according to claim 23, wherein the stepped opening has at leasttwo different diameters, one less than the diameter of the stabilizingelement, and, one greater than the diameter of the stem head.
 25. Amethod according to claim 24, wherein said elongated sleeve of saidstabilizing element is screwed into said bone opening at the diameterwhere said stepped bone opening is slightly smaller than that of saidelongated sleeve.
 26. A method according to claim 25, wherein said axialchannel in the stabilizing device is non-cylindrical, and wherein saidstabilizing element is screwed into said stepped bone opening by use ofan emplacement device fitted into said non-cylindrical axial channel.27. A method according to claim 21, wherein said insertion elementretaining said soft tissue is inserted forcibly into said stabilizingelement screwed into said stepped bone hole.
 28. A method according toclaim 21, wherein said stabilizing element comprises a flange at itsdistal end, whereby upon insertion of the stabilizing element in thebone opening, the flange is disposed at least partially outside the boneopening in a configuration whereby it will oppose further movement ofthe stabilizing element into the bone opening.
 29. A method foranchoring soft tissue within bone comprising. drilling an opening intobone; inserting into said bone a stabilizing element comprising anelongated sleeve with an axial channel extending therethrough; threadingsoft tissue through an aperture in an insertion element comprising anaperture containing stem head proximally located to an elongated stem,said stem having a diameter slightly larger than that of said axialchannel of said elongated sleeve; and pulling the distal end of saidinsertion element into proximal end, of said stabilizing element. 30.The method of claim 21 or 29, further comprising: drilling a secondopening into bone; inserting into said second bone opening a secondstabilizing element comprising an elongated sleeve with an axial channelextending therethrough; threading the soft tissue through an aperture ina second insertion element comprising an aperture-containing stem headproximally located to an elongated stem, said stem having a diameterslightly larger than that of said axial channel of said elongatedsleeve; and inserting the distal end of said second insertion elementinto proximal end of said second stabilizing element.
 31. The method ofclaim 30 wherein at least one of the stabilizing element and the secondstabilizing element comprises a flange at its distal end, whereby uponinsertion of the stabilizing element into a bone opening, the flange isdisposed at least partially outside the bone opening in a configurationwhereby it will oppose further movement of the stabilizing element intothe bone opening.
 32. A method for replacing a torn ligament comprising:obtaining a tendon graft; drilling a hole into bone; looping said tendongraft through an aperture in an insertion element; inserting astabilizing element comprising a sleeve with a cavity therein into saidhole; and inserting an insertion element comprising a stem with anaperture-containing stem head at the proximal end of said stem into saidstabilizing element.
 33. The method of claim 32 wherein said ligament isan anterior cruciate ligament and said bone aperture is in either afemur or tibia.
 34. The method of claim 32, further comprising: drillinga second opening into bone; inserting into said second bone opening asecond stabilizing element comprising an elongated sleeve with an axialchannel extending therethrough; looping the tendon graft through anaperture in a second insertion element comprising an aperture-containingstem head proximally located to an elongated stem, said stem having adiameter slightly larger than that of said axial channel of saidelongated sleeve; and inserting the distal end of said second insertionelement into proximal end of said second stabilizing element.
 35. Themethod of claims 21 or 32 wherein said stabilizing element is affixedinto bone by interference fit.
 36. The method of claims 21 or 32 whereinsaid stabilizing element comprises a flange at its distal end, wherebyupon insertion of the stabilizing element into a bone opening, theflange is disposed at least partially outside the bone opening in aconfiguration whereby it will oppose further movement of the stabilizingelement into the bone opening.
 37. A method for replacing a tornligament comprising: obtaining a tendon graft; drilling a hole intobone; looping said tendon graft through an aperture in an insertionelement; inserting a stabilizing element comprising a sleeve with acavity therein into said hole; and pulling an insertion elementcomprising a stem with an aperture containing stem head at the proximalend of said stem and any of an aperture, slot and barb at the distal endof said stem.
 38. The method of claim 37, further comprising: drilling asecond opening into bone; inserting into said second bone opening asecond stabilizing element comprising an elongated sleeve with an axialchannel extending therethrough; looping the tendon graft through anaperture in a second insertion element comprising an aperture-containingstem head proximally located to an elongated stem, said stem having adiameter slightly larger than that of said axial channel of saidelongated sleeve, and any of an aperture, slot, and barb at the distalend of said stem; and pulling the second insertion element into thestabilizing element.
 39. The method of claim 34 or 38, wherein saidligament is an anterior cruciate ligament, said bone opening is in afemur, and said second bone opening is in a tibia.
 40. The method ofclaim 34 or 38, wherein at least one of said stabilizing element andsaid second stabilizing element is affixed into bone by an interferencefit.
 41. The method of claim 34 or 38, wherein at least one of saidstabilizing: element and said second stabilizing element is affixed intobone by means of screw threads.
 42. The method of claim 34 or 38,wherein at least one of said stabilizing element and said secondstabilizing element comprises a flange at its distal end, whereby uponinsertion of the stabilizing element into a bone opening, the flange isdisposed at least partially outside the bone opening in a configurationwhereby it will oppose movement of the stabilizing element into the boneopening.
 43. A system for ligament reconstruction, comprising (a) atleast two bone anchors, each arranged for fixation to bone and eachcomprising an aperture, (b) a graft having at least two ends, at leastone having a filament extending therefrom, (c) the graft being threadedthrough the aperture of one of the anchors, (d) the filament affixingthe two ends of the graft to the aperture of the other anchor.
 44. Asystem for ligament reconstruction, comprising (a) at least two boneanchors, each arranged: for fixation to bone and each comprising anaperture, (b) a graft having at least two ends, at least one having afilament extending therefrom, (c) the graft being threaded through theapertures of each of the two anchors, (d) the filament affixing the twoends of the graft to each other.
 45. A system for ligamentreconstruction, comprising (a) at least a first and a second boneanchor, each arranged for fixation to bone and each comprising anaperture, (b) a graft having at least two ends, at least one having afilament extending therefrom, (c) the graft being threaded through theaperture of, the first anchor, (d) the two ends of the graft beingthreaded through the aperture of the second anchor, and (e) the filamentaffixing the two ends of the graft to the aperture of the first anchor.46. A system for ligament reconstruction, comprising (a) at least afirst and a second bone anchor, each arranged for fixation to bone andeach comprising an aperture, (b) at least a first and a second graft,each having at least two ends, at least one end of each graft having afilament extending therefrom, (c) the first graft being threaded throughthe aperture of the first anchor, (d) the filament of the first graftaffixing the two ends of the first graft to the aperture of the secondanchor, (e) the second graft being threaded through the aperture of thesecond anchor, and (f) the filament of the second graft affixing the twoends of the second graft to the aperture of the first anchor.
 47. Asystem for ligament reconstruction, comprising (a) at least a first anda second bone anchor, each arranged for fixation to bone and eachcomprising an aperture, (b) at least a first and a second, graft, eachhaving at least two ends, at least one end of each graft having afilament extending therefrom, (c) the first graft being threaded throughthe aperture of the first anchor, (d) the filament of the first graftaffixing the two ends of the first graft to the aperture of the secondanchor, (e) the second graft being threaded through the aperture of thefirst anchor, and (f) the filament of the second graft affixing the twoends of the second graft to the aperture of the second anchor.
 48. Thesystem of claim 43, 44, 45, 46, or 47, where at least one filament is asuture.
 49. The system of claim 43, 44, 45, 46, or 47, where the boneanchors are embedded in bone tunnels.
 50. The system of claim 49, wherethe bone tunnels are collinear.
 51. The system of claim 43, 44, 45, 46,or 47, where the graft is an autologous tendon graft. 52 The system ofclaim 51, where the graft is one of a length of semitendonosis tendonand a length of gracillis tendon.
 53. The system of claim 43, 44, 45,46, or 47 where the graft is an artificial tendon graft.
 54. The systemof claim 43, 44, 45, 46, or 47, where the system is for repair of theanterior cruciate ligament.
 55. The system of claim 43, 44, 45, 46, or47, where at least one of the bone anchors comprises a stabilizationelement adapted to be affixed in bone, and an insertion element adaptedto be inserted into the stabilization element.
 56. A method of ligamentreconstruction, comprising: (a) extending a filament from at least oneend of a graft having at least two ends, (b) threading the graft throughan aperture in a first bone anchor, (c) using the filament to affix thetwo ends of the graft to the aperture of the other anchor, (d) affixingthe first anchor in bone, and (e) affixing the second anchor in bone.57. A method of ligament reconstruction, comprising: (a) extending afilament from at least one end of a graft having at least two ends, (b)threading the graft through apertures in each of a first and a secondbone anchor, (c) using the filament to affix the two ends of the graftto each other, (d) affixing the first anchor in bone, and (e) affixingthe second anchor in bone.
 58. A method of ligament reconstruction,comprising: (a) extending a filament from at least one end of a grafthaving at least two ends, (b) threading the graft through an aperture ina first bone anchor, (c) threading the two ends of the graft through anaperture in a second bone anchor, (d) using the filament to affix thetwo ends of the graft to the aperture of the other anchor, (e) affixingthe first anchor in bone, and (f) affixing the second anchor in bone.59. A method of ligament reconstruction, comprising: (a) extending afirst filament from at least one end of a first graft having at leasttwo ends, (b) extending a second filament from at least one end of asecond graft having at least two ends, (c) threading the first graftthrough an aperture in a first bone anchor, (d) using the first filamentto affix the two ends of the first graft to an aperture of a second boneanchor, (e) threading the second graft through the aperture in thesecond anchor, (f) using the second filament to affix the two ends ofthe second graft to the aperture in the first anchor, (g) affixing thefirst anchor in bone, and (h) affixing the second anchor in bone.
 60. Amethod of ligament reconstruction, comprising: (a) extending a firstfilament from at least one end of a first graft having at least twoends, (b) extending a second filament from at least one end of a secondgraft having at least two ends, (c) threading the first graft through anaperture in a first bone anchor, (d) using the first filament to affixthe two ends of the first graft to an aperture of a second bone anchor,(e) threading the second graft through the aperture in the first anchor,(f) using the second filament to affix the two ends of the second graftto the aperture in the second anchor, (g) affixing the first anchor inbone, and (h) affixing the second anchor in bone.